1. Field of the Invention
The present invention relates to an asynchronous switch mode power supply, and particularly to such an arrangement comprising a closed loop arrangement in which the output is fed back to the input. The invention is particularly but not exclusively concerned with an envelope tracking power supply containing such an asynchronous switch mode power supply.
2. Description of the Related Art
Switch mode power supplies are well-known in the art. It is known in a switch mode power supply to provide a closed control loop, in which the output representing the selected supply voltage is fed back to the input, where it is compared with a reference signal. The control loop then acts to correct any error between the signal at the output and the reference (or target) signal.
In known prior art arrangements, synchronous operation is provided. Such known prior art arrangements provide synchronous control in which the switch mode power supply is typically a multi-level, multi-phase voltage converter. Different phases of a clock signal are used, in particular, to produce a finer phase/amplitude resolution than can be achieved with a single clock phase.
It is an aim of the invention to provide an improved switch mode power supply.